Using location information amongst wireless communication networks such as wireless wide area networks (WWAN), wireless local area networks (WLAN), cellular networks, and wireless personal area networks (WPAN) has become increasingly common. Moreover, obtaining measurements of distance between communication devices within a wireless network is advantageous, since the measurements of distance provide insight regarding wireless ranging.
Global positioning systems (GPS) can be used to provide accurate information regarding the position of a communication device, but this requires the communication device to implement GPS hardware, thereby adding cost and complexity. Since GPS typically provides poor performance indoors, the use of GPS location for communication devices can be impractical. Therefore, signal strength is often used to determine distance measurements. More specifically, wireless devices typically perform calculations to determine a received signal strength indicator (RSSI). Using free space propagation loss calculations, a distance between two wireless communication devices can then be determined. But signal strength measurement distance calculations do not provide high accuracy distance measurements, since other factors can impact signal strength measurement, such as interference and/or the presence of other signals in the same or a nearby frequency band.
Therefore, another method to perform distance measurements utilizes the calculation of propagation time using timestamped time of arrival (ToA) and time of departure (ToD) information exchanged between two or more communication devices. Using the propagation time and the known speed at which the signal travels through the respective medium, a distance between the two communication devices can be calculated.
However, due to delays in the communication system, such as processing delays and/or signal group delay, timestamp calculations typically only provide accuracies resulting in a measurement resolution of 10 nanoseconds (ns) or more. As a result, distance calculations based on these timestamps can only determine a location of a communication device to within about 10 feet.